Trialkylsiloxanes and their production



United States Patent O 3,012,052 TRIALKYLSILOXANES AND THEIR PRODUCTIONWalter Simmler, Koln-Mulheim, Germany, assignor to Farbenfabriken BayerAktiengesellschaft, Leverkusen, Germany, a corporation of Germany NoDrawing. Filed Aug. 11, 1958, Ser.No. 754,127 Claims priority,application Germany Aug. 20, 1957 Claims. (Cl. 260-4483) The inventionrelates to the production of new siloxanes of the formula wherein Rdenotes an alkyl radical, especially methyl, R denotes an aryl radical,especially phenyl, and n is the number 1, 2 or 3. If R denotes methyland R denotes phenyl, the formula comprises the compoundstris-(trimethylsiloxy monophenylsilane,tetrakis-(trimethylsiloxy)-l,2-diphenyl-disiloxane andpentakis-(trimethylsiloxy) -l ,2,3 -triphenyl-trisilox ane.

According to the invention, these compounds are prepared in such amanner that mixtures of more than 1 mol and at most 3 mols of ahydrolyzable trialkylsilane and 1 mol of a hydrolyzable monoarylsilaneare slowly reacted with as many moles of water as gram-atoms of oxygenare stoichiometrically required for the formation of the siloxane bonds.The water is either added dropwise or injected or combined by means ofspraying nozzles with the likewise sprayed silane mixture which may bediluted with a solvent. The reaction is carried out at about roomtemperature; when chlorosilanes are employed, external cooling isrendered unnecessary by the evaporation of the hydrogen chloride formedduring the reaction.

It is known that in the hydrolysis of silane mixtures which also containaryl-substituted silanes, the difiiculty is encountered of preventingthe precipitation of solid, solely aryl-substituted silanols andsiloxanes. It is surprising that in the hydrolysis according to theinvention siloxanes tree from appreciable portions of silanols areobtained without loss of arylsiloxane units by separation.

The new siloxanes according to the invention are va1uable oils which areadvantageously used as heat-transfer agents, as liquids in thermometersand thermo-regulators, especially because their coefficient of expansionis little dependent on the pressure.

They are also extremely suitable as working fluid for high vacuumdiifusion pumps. It has been found that these new oils have an extremelysteep rise of their vapour pressure with rising temperature as againstcomparable known fluids for high vacuum pumps consisting of phenylmethylsiloxanes of a different structure. This means 3,012,052 Patented Dec.5, 1961 that, compared with other polysiloxane oils having the samevapour pressure at the condensing surface temperature of the pump, theoils according to the invention may more easily be evaporated because ata given pressure a lower temperature is required for their evaporationin the boiling vessel of the pump, thus involving a smaller loss ofenergy and greater protection of the pump, or because at a giventemperature in the boiling vessel a more convenient pre-vacuum ofbetween the fivefold and the tenfold pressure may be applied. Whencomparing them with the other'oils at the same pressure and at the sametemperature in the boiling vessel, a better final vacuum is thusattained.

final boiling vacuum temperature mm. Hg 1 at 1 Hg,

trisltrimethylsiloxy) -monphenylsilane 10- to 10- 105tetrakis-(trimethylsiloxy)-l,2-chphenyldisiloxane 1|)- to 10- 175pentakis-(trlmethylsiloxy)-l,2,3-triphenyltrisiloxane 10- to 10- 220illustrating the invention.

EXAMPLE 2.61 kilograms of trimet-hylmonochlorosilane and 1.69 kilogramsof phenyltrichlorosilane (molecular ratio 3:1) are placed in a l0-litrefive-neck flask provided with stirrer, 2 condensers and a thermometer,and 0.45 kilogram of water injected with intensive stirring in thecourse of 3 hours. While the reaction proceeds, the mixture is cooled toa temperature below room temperature and hydrogen chloride escapes. Themixture is then heated to 100 C. for a further hour to expel thedissolved hydrogen chloride, aud the residuary HCl is subsequentlyneutralized with sodium carbonate or an alco-- holic sodium hydroxidesolution. After filtration, the crude product is obtained in a yield ofbetween to percent, and the compounds listed in Table l are obtained byfractional vacuum distillation.

When the molecular ratios of trimethylnronochlorosih ane and water arechosen at 422:5 or 5 23:7 etc. instead of 3:1:3 and the process isotherwise carried out as described above, there are obtained the yieldslisted in Table 2 of the individual compounds M (TM) wherein M denotesthe siloxane unit (CH SiO and T denotes the siloxane unit H C SiO Table1 Molecular Percent 0 Percent H weight Boiling point n Compound TypeFormula (1 m n Hg) Calcd. Found Calcd. Found Galcd. Found 1Tris-(trimethylsiloxy)-phenylsilane MsT CraHazOaSls- 37.? 365 48. 4 48.6 8. 6 8. 4 2 Tetrakis (trimethylsiloxy)- 1,2diphenyl-disiloxane M T C HO5Sn 583 575 49. 4 49. 2 7. 9 7. 6 3 Pentakis (trimethylsiloxy)-1,2,3-tripheuyl-trisilorane M5T3 G33HmO7Sla--- 793 782 50. O 50.0 7.6 7.8 220 4 Hexakis (trimethylsiloxy)- 1,2,3,4 tetraphenyl trisiloxane M51,CuH mSim- 1003 976 50.2 49. 9 7. 4 7. 7 255 Table 2 YIELDS DEPENDENT ONMOLAR RATIO OF COMPONENTS Molar ratio +residue Mixture in kg. ofMBaSiCH-PhSiClz-f-HzO IVleaSiCl: PhSlClal H O Percent Percent PercentPercent came: mono Lo sin; .1

wherein R represents an alkyl radical, R represents an aryl radical andn is one of the numbers ,1, land 3, which comprises preparing a mixtureof a trialkylmonochlorosilane and a monoaryltrichlorosilane in aproportion of more than 1 mol and at most 3 mols of the former for eachmoi of the latter, slowly adding water to said mixture in an amount of ahalf mol of H 0 for each gramatom of chlorine in the sum of saidchlorosilanes, and then heating the mixture to about 100 C. until theevolution of hydrogen chloride is substantially completed.

2. The process according to claim 1, which comprises adding said waterto said mixture at such a rate that the temperature thereof does notexceed room temperature.

3. The process according to claim 1, which comprises SiR;

adding said water to said mixture under external cooling and therebymaintaining temperature of the mixture below room temperature.

4. Pentakis (trimethylsiloxy) 1,2,3 triphenyltrisiloxane of boilingpoint 220 C. at 1 mm. Hg.

5. A working fluid for a high vacuum diffusion pump, consistingessentially of pntakis-(trimethylsiloxy)4,2,3- triphenyltrisiloxane.

, References Cited inthe file of this patent UNITED STATES PATENTS OTHERREFERENCES Meads et al.: Jour. Chem. Soc. (London), vol. 107, (1915),pp. 459-68.

Andrianov et a-l.: Jr. Obschei Chimie, SSSR, vol. 28, No. 2, February1958, pp. 33336.

UNITED STATES PATENT'OFFICE CERTIFICATE OF CORRECTION Patent N0.3,01'2,052

December 5, 1961 Walter Simmler It is hereby certified that errorappears in the above numbered pat ent requiring correction and that thesaid Letters Patent should read as corrected below In the heading to theprinted specification, line 7, for

"Aug. 20, 1957-" read Aug. 17, 1957 column 1, lines 21 and 22, after"trimethylsiloxy" insert a closing parenthesis; column 2, line 51, after"ane" insert phenyltrichlorosilane I Signed and sealed'this 24th day ofApril 1962.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L, LADD Attesting Officer Commissioner of Patents

1. A PROCESS FOR THE PRODUCTION OF TRIALKYLSILOXYMONOARYLSILOXANES OFTHE GENERAL FORMULA
 4. PENTAKIS - (TRIMETHYLSILOXY) - 1,2,3 -TRIPHENYLTRISILOXANE OF BOILING POINT 220*C. AT 1 MM. HG.